mainboard: Add Sapphire Pure Platinum H61

This board has a socketed SOIC-8 4 MB flash chip. All the flash regions are unlocked by default but unfortunately flashrom doesn't work with the original firmware and the stock UEFI flash tool refuses to flash the coreboot image (different image ID). For now, the external programmer seems to be the only option for the first coreboot flashing.

Issues:- The USB is always powered, even is S3 and S5 (like in the original firmware).- Internal flashing with flashrom doesn't work after resuming from S3.- The raminit is unreliable, as the RAM training sometimes fails and sometimes succeeds, with the same couple of RAMs. Once a MRC cache has been created, the raminit works fine.- If an external card is inserted and the option ONBOARD_VGA_IS_PRIMARY is not enabled, the internal GPU disappears completely from the PCI bus.